As far as I have been able to determine, neither James Mulligan, Jim Stockdale nor Jeremiah Denton considered McCain to have behaved dishonorably while he was a POW. I was not there to witness his behavior - they were. Their opinions on that issue are [more than] good enough for me.
However, I do think John McCain has behaved dishonorably as a U.S. senator. My own eyes and ears tell me that.